This invention relates to method of incorporating a density modifier into an absorbent composite. The resulting absorbent composite is suitable for use in personal care absorbent articles, which are particularly adapted for absorbing various blood-containing bodily fluids, such as diapers and catamenial articles including sanitary napkins and pads, tampons, wound dressings, and the like.
A wide variety of disposable absorbent articles for collecting bodily fluids are known in the art. Commercial absorbent articles include diapers, sanitary napkins, training pants, and incontinent care pads, wound dressings, tampons, and the like. Disposable products of this type include some functional elements for receiving, absorbing, and retaining fluids. Typically, such absorbent articles have an absorbent core containing cellulosic fibers, for example, wood pulp fluff, particles of highly absorbent materials, for example, superabsorbents, and an admixture of cellulosic fibers and superabsorbents. Typically, such articles include a fluid-permeable cover sheet or topsheet which typically faces the body of the user, an absorbent core, and a fluid-impermeable backsheet.
Cover sheet materials are utilized for the transport of bodily fluids into the absorbent core of personal care absorbent articles and, thus, materials used for cover sheet applications must manage distinctly different body excretions, depending upon the application and the product type. Some products must manage fluids, such as urine, while others must manage proteinaceous and viscoelastic fluids, such as menstrual discharge and fecal matter. The management of viscoelastic menstrual discharge by feminine care products such as sanitary pads and napkins is exacerbated due to the variations in composition and rheology over a broad range of elasticity. Fluid management in feminine care applications requires control of absorption of bodily fluids, control of fluid retention in the cover, control of stain size and intensity, control of rewet of fluid back to the surface, and control of the release of fluid to the absorbent core.
There are several factors which influence the flow of liquids in fibrous structures including the geometry of the pore structure in the fabrics, the nature of the solid surface (surface energy, surface charge, etc.), the geometry of the solid surface (surface roughness, grooves, etc.), the chemical/physical treatment of the solid surface, and the chemical nature of the fluid. One problem associated with absorbent articles intended for use in handling fluids comprising blood components such as feminine care products and wound dressings is the tendency of red blood cells to block the pores of the materials used for absorption of fluids in such products. Typical of such porous materials are nonwoven or fibrous web materials. The blockage of the pores of the nonwoven or fibrous web materials by the red blood cells results in a reduction in the fluid intake and the wicking capabilities of such products. In addition, in the case of feminine care products such as sanitary pads, napkins and tampons, the blockage of pores of nonwoven materials used therein by red blood cells results in increased staining. In the case of feminine care products comprising superabsorbents, the red blood cells attach themselves to the superabsorbents, resulting in blockage of the superabsorbents and a significant reduction in fluid uptake.
In the case of feminine care products such as sanitary pads and napkins, women have come to expect a high level of performance in terms of comfort and fit, retention of fluid, and minimal staining. Of utmost importance, leakage of fluid from the pad onto undergarments is regarded as totally unacceptable.
Improving the performance of feminine care products continues to be a formidable undertaking, although numerous improvements have been made in both their materials and structures. However, solutions addressing the issues arising from the presence of red blood cells in blood or menses in feminine care products, as well as other absorbent materials for handling blood-containing fluids, have not been satisfactorily implemented. It is apparent that a system which effectively handles red blood cells in a manner which addresses the issues set forth hereinabove will not only improve the distribution of incoming fluids by the absorbent material, but will also reduce the tendency toward premature failures of these absorbent articles. Furthermore, such a system that can be incorporated into a thin, discreet product that can readily absorb a large amount of such fluids would be a remarkable improvement over current absorbent systems.
Another obstacle that stands in the way of improving the performance of feminine care products is the difficulty of incorporating fluid treatment agents into absorbent composites. One method of applying fluid treatment agents to absorbent composites that has been used with success involves soaking an airlaid handsheet in the fluid treatment agent, squeezing out the excess solution, and then drying the handsheet in an oven. This approach works well for small scale production. However, it does not work for large scale production because drying the airlaid slows down the production process significantly.
There is a need or desire for a method of incorporating fluid treatment agents into absorbent composites.
In response to the discussed difficulties and problems encountered in the prior art, a new method of incorporating fluid treatment agents into absorbent composites has been discovered.
The present invention is directed to a method of incorporating a fluid treatment agent, namely a density modulator, into an absorbent composite. The method includes the steps of applying a density modulator solution to a pulp sheet. The application may be carried out by slot coating or by using a flooded nip. The pulp sheet is then fiberized. Finally, the fiberized pulp sheet is incorporated into an absorbent composite. The concentration of the density modulator solution is an important consideration. Suitably, the concentration of the density modulator solution is between about 5% and about 25%, or between about 8% and about 20%, or between about 10% and about 15% by weight of the pulp sheet.
By applying the solution to the pulp sheet in this way, the liquid is dried by the heat of the fiberizer and is uniformly distributed throughout the pulp. Also, by using more than one forming head, layers of treated material can be made. In addition, the method of this invention allows for incorporation of the density modulator into airlaid or fluff, whereas the other methods do not.
The density modulator makes the treated material in the absorbent article more wettable, thus increasing the article""s intake capability, and also lowers the density of the treated material when the material comes into contact with a blood-containing fluid. By lowering the density of the treated material, the volume of the material increases, thereby providing more space in which the fluid can be contained.
The density modulator can be alkyl glycoside or any other composition that increases wettability and lowers density upon contact with blood-containing fluid. Another feature of the density modulator is that it is present in a low enough concentration that it provides wettability and affects the density of the material to which it is applied without lysing the red blood cells with which the treated material comes into contact.
In one embodiment of the invention, the absorbent composite with the density modulator incorporated therein is used to form an absorbent article, such as a catamenial device. More particularly, the absorbent composite can be used to form a liner or a containment layer, or both the liner and the containment layer.
One of the benefits of this invention derives from the fact that the red blood cells of a blood-containing fluid, having come into contact with the density modulator, are no longer able to block the flow of fluids into any superabsorbents that may be present in the absorbent material.
With the foregoing in mind, particular embodiments of the invention provide a method of making absorbent composites that are thin and discreet, can effectively handle red blood cells, and can readily absorb a large amount of blood-containing bodily fluids.